In the manufacture of integrated circuits (ICs) and other electronic devices, testing with automatic test equipment (ATE) is performed at one or more stages of the overall process.
A special handling apparatus is used to place one or more devices under test (DUT or DUTs) into position for testing. In some cases, the special handling apparatus may also bring the DUT or DUTs to the proper temperature and/or maintain it at the proper temperature to be tested. The special handling apparatus is of various types including “wafer probers” or “probers” for testing unpackaged devices on a wafer and “device handlers” or “package handlers” for testing separated or non-separated packaged parts; herein, “peripheral” or “peripherals” will be used to refer to all types of such apparatus. Also the acronym DUT may be used to refer to either a single device under test or a set of devices simultaneously under test.
The electronic testing itself is provided by a large and expensive ATE system. The DUT requires precision, high-speed signals for effective testing. Accordingly, the “test electronics” within the ATE, which are used to test the DUT, are typically located in a “test head,” which must be positioned as close as possible to the DUT. The test head is extremely heavy: the size and weight of the test heads have grown from a few hundred pounds to as much as three to four thousand pounds.
In order to use a test head to test integrated circuits, the test head is typically “docked” to a peripheral. When docked, the test head must be located as close as possible to the peripheral's test site in order to minimize signal degradation. A test head positioning system, including a test head manipulator and a docking apparatus, may be used to position the test head with respect to the peripheral and may be designed to facilitate flexible docking and undocking of a test head with a variety of peripherals. With the test head in docked position, a batch of devices, generally all of the same type, may be tested. In general a set of DUTs are tested simultaneously in parallel. Depending upon the overall system the number of DUTs in a set may range from one to 16 or more in a packaged device handler. In wafer probing the number of devices tested at one time has grown to dozens with an ultimate goal of testing all devices on the wafer in parallel. The peripheral places each set of DUTs in turn in position to be tested. For the purposes of this document “DUT” will hereinafter refer to either a single device under test (i.e., a set of one) or a set comprising a plurality of devices to be tested simultaneously.
After the testing of a particular DUT type is complete, the test head may be undocked from the peripheral and moved away from using a test head manipulator. If desired, another DUT type may be loaded into the peripheral, and the test head is docked again to the peripheral to perform electronic testing. When changing over from testing one type of device to another, it is usually necessary to reconfigure the system by changing one or more units such as Performance Boards, DUT boards, and/or probe cards which adapt the test head and peripheral to the particular DUT. More will subsequently be said about such units.
It is furthermore often desirable to dock a given test head with different peripherals from time to time. For example, testing may be performed with a certain packaged device handler for a time, and then it may be desired to change to another packaged device handler. In other situations, it may be desired to change over from a wafer prober to a packaged device handler or conversely. In such cases the test head is undocked from the original peripheral, which is then moved out of the way. The new peripheral is then moved into place, and the test head is docked with it. In other situations both peripherals are in position to be used, and the test head may be undocked from the first peripheral and then moved to and docked with the second peripheral. It is often also desirable to move the test head away from a peripheral to perform maintenance. Thus, it may be required to easily dock and undock the test head with a variety of different peripherals. In all of these situations the heavy test head is typically maneuvered from position to position using a test head manipulator.
An electrical “interface system” or “interface” connects the test head with the peripheral's test site where the DUT is electrically tested. Generally, a performance board is attached to the test head to adapt the test head to a particular type of DUT or family of DUT types. The performance board generally includes conductive paths from the test electronics in the test head to a set of conductive pads arranged in a planar pattern. A second board for contacting the DUT is also provided. If the testing is performed on a prober type of peripheral, the DUT-contacting board is typically a probe card having needle like conductive contacts used to make electrical connection to the tiny connection pads on the chip itself. If packaged parts are tested using a handler, a DUT board including suitable contact devices to electrically connect with the “pins” of the DUT is used. Thus, a DUT board might include an appropriate test socket. In many situations the probe card or DUT board has conductive pads in a planar pattern that is the same as that of the DIB or load board. An interface system provides mechanical coupling and electrical interconnections between the performance board and the DUT-contacting board. In many situations the DUT-contacting board may be held in place by the interface unit which in turn is secured to the peripheral. In other situations the DUT-contacting unit may be held by the peripheral and the interface is separately aligned and secured to the peripheral. Typically, spring-loaded electrical contacts, commonly known as spring pins or Pogo Pins®, are disposed on each side of the interface to provide the electrical signal paths between the conductive pads on the probe card or DUT board and the conductive pads on the DIB or Load Board attached to the ATE. In situations where the contact patterns on the performance board are the same as on the DUT-contacting board, double-ended, spring pins may be used to realize the signal paths and electrical contacts. The interface may include hundreds or thousands of such electrical contacts, which are of necessity small and fragile. Typically, the contacts are arranged in a generally planar fashion on each side of the interface. When the test head is docked to the peripheral through the interface, electrical connections are thus made by the contacts on the two sides of the interface between the probe card or DUT board and performance board attached to the test head.
A typical interface common in the art is an apparatus with two hingeably connected units. The bottom unit or first unit attaches to the peripheral and holds the probe card or DUT board in a proper alignment for testing. The lid unit, or second unit, contains the electrical contacts used to complete the electrical signal paths between the probe card or DUT board and the performance board attached to the test head. Preparation for testing begins with the interface attached to a peripheral by the first unit and in an open position. A probe card or DUT board is placed into the first unit, properly aligned, and secured. A performance board is attached to the test head. The second unit is then pivoted towards and locked against the first unit to bring the electrical contacts on the one side of the second unit into contact with the probe card. The test head is then docked to the peripheral, making contact between the electrical contacts on the other side of the second unit and the conductive pads on the performance board, thus completing the electrical connections between the test head and the peripheral's test site. The DUT is then positioned for testing by the peripheral, completing the connection between the DUT and the test head; and the electrical signal tests are then run. Once testing is complete, the test head may be undocked from the peripheral. The interface is unlocked, and the second unit is moved away from the first unit. The probe card or DUT board may be removed to allow for installation of another probe card or DUT board for testing further device types.
It is well understood that, when docking the test head, the test head is typically first planarized with respect to the interface, aligned linearly in two dimensions, and aligned rotationally about an axis perpendicular to the plane of the interface. The test head may then be advanced along a linear path into a docked position. The docking apparatus desirably provides a means to establish the final docked distance (or “height”) between the test head and the peripheral such that the electrical contacts are satisfactorily mated (that is, with sufficient compression, to assure a low resistance connection) and such that the test head does not over-travel and thus damage or destroy the contacts. Interfaces are typically changed when operation is switched from one peripheral to another; indeed, each peripheral may have its own interface attached to it. Further, it is typical that when a single peripheral is used to first test devices of one type and then reconfigured to test devices of another type, the interface may either be changed from a first type to a second type or the probe card (or DUT board) may be changed from a first type to a second type. Generally, the docked height requirement may be different for each testing set up. It is most desirable to have a system where an interface may remain in place on the peripheral and to have a capability to easily change probe cards and/or to reconfigure the interface to change over from one DUT type to another.
The prior art is described with reference to FIG. 16. FIG. 16 has been adapted from U.S. Pat. No. 6,114,869. Referring to FIG. 16, signal interface system 1 includes a first ring unit 3 attached by hinge assembly 8 to second ring unit 11. Second ring unit 11 includes spring-loaded contacts 42. When the interface is closed, spring-loaded contacts 42, held in “POGO tower” 10 engage fixed conductive pads 55 contained on probe card (or DUT board) 6, which is contained in first ring unit 3. As is generally well known and discussed in the '869 patent, it is preferred that when closing an interface of this type second ring unit 11 is first pivoted downwards to a position where the plane of spring-loaded contacts is parallel to the plane of contacts in first ring unit 3. Then the plane of spring-loaded contacts in second ring unit 11 is moved vertically downwards to make compressive contact with the contacts of first ring unit 3. In opening the interface, the reverse procedure is preferred. In this way the contacts are not scraped against one another in a destructive manner. This is accomplished in the interface of FIG. 16 by mounting “POGO tower” 10 to second ring unit 11 with springs. A fixed hinge enables second unit 11 to be rotated to a position where the plane of the spring-loaded contacts 42 is essentially parallel to and spaced slightly apart from the plane of conductive pads 55. Rotating lock ring 16 by means of handle 4 moves “POGO tower” 10 downwards or upwards respectively bringing spring-loaded contacts 42 into or out of engagement with conductive pads 55. Although this approach is protective of the contacts in normal operation, it is disadvantages in the event second unit 11 is closed abruptly with excessive force (i.e., slammed shut) in which case POGO tower 10 may bounce to such a degree that contacts 42 could be damaged. Additionally, repeatability of planarity between contacts 42 and conductive pads 55 prior to rotating handle 4 is dependent upon the mounting springs having uniform characteristics throughout their lives.